1. Field of the Invention
This invention concerns improved feeding and carrying grippers for weaving machines, in particular, feeding and carrying grippers, the former being designed to guide a weft thread through the first half of a shed gap, and the latter to guide a weft thread through the second half of the gap.
In particular, the invention concerns a clamping device for weft threads which can be embodied in each of these grippers.
2. Description of Prior Art
It is known that an important cause of malfunctions in gripper weaving machines is the loss of the weft thread from the clamping device of one or both feeding and carrying grippers. This problems occurs most frequently because the clamping devices of the existing grippers do not react in an optimal manner to the different types of weft yarn; for example, different thickness yarns, or are not suitable to clamp the weft thread in an effective and reliable manner, when there are differences in the tension in the weft thread in the face of vibrations in the weaving machine.
Efforts have been constantly made to develop grippers with improved clamping devices. Improved grippers for weft gripper weaving machines are known in which the clamping device consists of two components pressed together by means of a resilient component, such that the contact surfaces of these components form a wedge-shaped opening in order to permit feeding of the weft thread to the contact area of the components pressed together. In this case, one of these components is usually firmly fastened to the body of the grippers, while the other component is moveable along the first, and can, for example, rotate or slide relative to it. The components can also be resilient relative to one another.
In a known alternate of this embodiment, the contact surface of one of the two components is provided with a compressible material.
A disadvantage of this known embodiment lies in the fact that the contact surfaces of the components involved do not usually offer a perfect joint as a result of tolerance deviations, so that it is impossible to clamp the weft yarn with a fixed or constant force.
In order to find a solution for this problem, weft grippers were devised in which the clamping device consists of two components which are pressed together by means of a resilient component, with the characteristic that at least one of the contact surfaces formed between the two aforementioned components is L-shaped.
These devices have the disadvantage that the weft thread, when clamped, is folded out of true, such that it is usually damaged, and is prone to breakage.
Grippers are also known in which the clamping devices are provided by opposed V-shaped profiled contact surfaces, wherein one of the contact surfaces has a V-shaped recess, while the other contact surface is formed of a V-shaped projection.
This type of device also presents the disadvantage that, in the event of the slightest irregularity during the weft feeding cycle, the weft thread will be damaged or broken.